Updated your iPhone 3GS to iOS 5.1 with baseband 5.16.05 and need to unlock it? There’s still hope if you don’t mind using the dreaded iPad baseband 6.15.00.

UPDATE: If you’re using an AT&T iPhone, you can officially unlock it now so that you won’t to do all these. Click here.

Currently, the jailbreak for iOS 5.1 is tethered (except if you have an old bootrom), which means you will need to use a computer to boot up your iPhone 3GS. There’s no unlock for modem firmware or baseband 5.16.05. To be precise, there’s no ultrasn0w unlock since baseband 5.14.02.

10. Before restoring, ‘pawn’ DFU your iPhone to allow it to accept custom firmware. Otherwise, you will get error 16xxx. Sn0wbreeze will guide you how to pawn DFU your iPhone using iREB or just search on YouTube.

11. Launch iTunes 10.6, press shift on your keyboard and then click on Restore. Point it to the custom firmware on your desktop. Wait until the restore is complete. Your iPhone will boot up and you’re ready to unlock it once you’ve gone through the setup process. Just to be sure, go to Settings, General, About and check that your Modem Firmware (baseband) should show 6.15.00.

At posting time, the latest ultrasn0w is not yet supported on iOS 5.1. You must intall an ultrasn0w fixer patch first.

12. If you’ve installed ultrasn0w, remove it now.

13. Launch Cydia.

14. Add the following to your source:

http://repo.iparelhos.com

15. Tap on the iParelhos repo to see Ultrasn0w Fixer utility. Tap install to begin installation.

16. Once installation is complete, we need to install ultrasn0w. Launch Cydia.

17. Search for ultrasn0w on Packages in Cydia. If you cannot find it, add new sources by typing ultrasn0w repo:

Phewwww – had iphone 3gs 4.3.3 06.15.00 and had installed ipad baseband. After searching frantically as the phone would not get back the dfu stage to restore it back to 4.3.3 i instead followed these instructions to a tee and worked perfectly. Unlocking and everything works perfect. You my friend are a star!!

i, Ive restore with this custom firmware 5.1 preserving my baseband to 3.10 and my network is always unavalable what should I do ? Download Ultrasnow ? 5.0.1 really sux … Pleaze Help me, I cant unlock it, fix for ultrasnow doesnt work so I try this method ..

followed all the suggestions,had official unlock approval, contacted my unlock provider, suggested deleting and or turning off, with redsn0w or sam , what ever, obviously a flashed baseband–for unlock purposes, early 3gs, will experience an issue when using ITunes for the official ATT unlock, so>>>>>> now what? Buy a new phone<<<>>> suggestions

From Ecuador,
I followed every step and it worked great, thannnnnnnnnnnnnnnnnnnnnnnnks. I owe you a beer!
my phone was given to me by my sister. It updated by ignorance to 5.1.1 and so it did its baseband to 5.16.05.